With recent progress and spread of personal computers, a large number of hard disk apparatuses have been used as external storage units because of the advantage of their large capacity and high speed. At the same time, recent increase in the size of computer software and in the amount of handled data has caused the necessity of much larger capacity in hard disk apparatuses serving as external storage units.
In addition to the case of computers, also in digital AV equipment for recording and reproducing video and audio data by means of digital technology, the use of hard disk apparatuses is gradually increasing because of the advantage of their large capacity and high speed. Also in this application, hard disk apparatuses of much larger AV data of huge size.
Described below is a prior art system for recording and reproducing AV data.
FIG. 13 shows the configuration of a hard disk apparatus composed of a prior art hard disk drive (HDD) 10 and a personal computer (PC) 60. Here, the PC 60 is a personal computer for processing AV data in real time.
A magnetic disk 23 is a magnetic recording medium for recording data.
A magnetic head 24 is means of recording and reproducing information to and from the magnetic disk 23.
An actuator 25 is means of positioning the magnetic head 24 at an arbitrary radial position on the magnetic disk 23 with the magnetic head 24 at the tip.
The actuator 25 comprises a carriage 25a, a suspension 25b, a drive coil 25c, a permanent magnet 25d, and so on.
The carriage 25a is means of rocking around a fulcrum at point c.
The suspension 25b is attached to the carriage 25a, and is means of maintaining the magnetic head 24 in a levitated state a few tens nanometers above the surface of the magnetic disk 23 by means of a levitation mechanism called a slider.
The drive coil 25c is means of generating a driving force in cooperation with the permanent magnet 25d arranged opposingly thereto, and thereby causing the actuator 25 to rotate or rock.
The permanent magnet 25d is means of generating the driving force in cooperation with the drive coil 25c, and thereby causing the actuator 25 to rotate or rock.
A head amplifier 27 is means of detecting and amplifying a reproduced signal from the magnetic head 24, and of amplifying a recording signal.
A controller 26 is means of: detecting the position of the magnetic head 24 relatively to the magnetic disk 23 on the basis of the output from the head amplifier 27; outputting to a driver 28 a control signal for positioning the actuator 25 to a predetermined position on the magnetic disk 23; converting a signal read from the output of the head amplifier 27, into digital data; and converting digital data to be recorded, into a signal to be written in, and then providing the signal to the head amplifier 27.
A driver 28 is means of providing a current corresponding to the control signal, to the actuator 25.
An interface 29 is means of transmitting and receiving digital information to and from the PC 60.
A buffer cache 30 is means of storing such information and thereby improving the efficiency of the recording and reproducing in the magnetic disk 23.
Although not shown in the figure, the system further comprises: a spindle motor for driving the revolution of the magnetic disk 23; a buffer control unit for controlling the buffer cache 30; and an information recording and reproducing circuit.
FIG. 14 shows the magnetic disk 23. The surface of the magnetic disk 23 is partitioned into tracks 62 each of which is a concentric region for recording data. Each track 62 is, in turn, partitioned into sectors 63. Each track 62 is provided with a sequential track number starting from the inside or the outside. Accordingly, each recording segment on the magnetic disk 23 is specified by the combination of a track number and a sector number. As such, in the HDD 10, access is carried out on a sector 63 basis. Accordingly, when a set of AV data is composed of a plurality of sectors 63, these sectors 63 are not necessarily arranged within the same track 62 or within adjacent tracks 62. That is, in some cases, a set of AV data can be distributed into non-consecutive sectors 63.
Further, the magnetic disk 23 has a region called an alternate region in addition to the recording region for AV data. Sectors within the alternate region are called alternate sectors. The alternate region is provided, for example, in the inner circumference portion of the magnetic disk 23. The alternate sectors are used as replacements of defective sectors, when defective sectors in which recording and/or reproducing are not carried out normally occur in the magnetic disk 23.
Described below is the operation of the prior art system for recording and reproducing AV data.
First, described below is the operation of recording to and reproducing from the magnetic disk 23 by the HDD 10.
In the recording or reproducing of AV data, the magnetic head 24 moves to (seeks) a track where AV data is recorded. Then, the magnetic head 24 waits for the rotation of the magnetic disk 23 until an appropriate sector for recording or reproducing comes under the magnetic head 24. After that, the recording or reproducing of the AV data is started.
At this time, consecutive sectors can be read out continuously without magnetic head 24 movement or rotation waiting. In contrast, read-out from non-consecutive sectors needs the three repeated processes of magnetic head 24 movement, rotation waiting, and data read-out. That is, the time of magnetic head 24 movement and rotation waiting, during which data cannot be read is necessary as an extra time, in comparison with the case of consecutive sectors.
Thus, when a large amount of data such as video and audio data is transferred successively for a long time, and when the data is recorded and reproduced, the data is recorded in a distributed manner over a plurality of tracks. This causes the necessity of track jump actions (seek actions) from a track to another track and rotation waiting, during the recording and reproducing. Since recording and reproducing data is not performed at all in such a period, the rate of recording and reproducing a large amount of data which is transferred successively is reduced, and the transfer performance is degraded.
When the track jump action is carried out normally, the next recording or reproducing can be started after the above-mentioned time. Nevertheless, settling operation for damping residual oscillation after the track jump takes a substantial time in some cases. During this operation, the starting point for the next recording or reproducing can pass by. In this case, the system needs to wait for the next turn of disk rotation. This degrades the transfer performance further.
Accordingly, in the recording and reproducing of video and audio data, continuous transfer performance is essential, because in the above-mentioned cases, the video and audio reproduction can stop temporarily (frame drop)
Described below is an example of operation in which continuous transfer performance of AV data is ensured. In this example, the PC 60 records AV data into the HDD 10, and at the same time, reproduces the AV data having been recorded in the HDD 10.
When AV data is recorded and reproduced as an MPEG-2 transport stream, the PC 60 transfers the data to the HDD 10 on a GOP (group of picture) basis.
That is, in the recording of AV data transmitted from an external device at a rate of 30 frames per second, the PC 60 stores the AV data successively into a buffer 76 provided in the main memory.
Then, when a complete GOP is stored in the buffer 76, the PC 60 transfers the GOP to the interface 29 of the HDD 10, and then issues a record command.
FIG. 15(a) shows a 1GOP 64 as an example of a GOP. A GOP is treated as a unit in the editing of AV data, and includes necessarily an I-frame. In the example shown in FIG. 15(a), the 1GOP 64 contains the frames of I, B, B, P, B, . . . in this order. A GOP contains AV data for 0.5 second or the like. That is, when the AV data is at the rate of 30 frames per second, each GOP contains 15 frames. In case of AV data for ordinary resolution televisions, the size of a GOP is generally from 512 Kbytes to 1 Mbytes. In case of AV data for high definition televisions, the size is from 1.5 Mbytes to 2 Mbytes.
The size of a GOP is variable. Thus, when the PC 60 transfers the AV data of the 1GOP 64 to the HDD 10, fixed length data is formed by adding dummy data 65 to the 1GOP 64, as illustrated by a fixed length block 66 in FIG. 15(b). The PC 60 transfers the fixed length block 66 to the interface 29.
In case of AV data for ordinary resolution televisions, the size of the fixed length block 66 is assumed to be, for example, 1 Mbytes. In case of AV data for high definition televisions, the size of the fixed length block 66 is assumed to be, for example, 2 Mbytes.
On receiving the record command issued from the PC 60 via the interface 29, the controller 26 records the data of the fixed length block 66 onto the magnetic disk 23.
In contrast, in the reproducing of the AV data, the PC 60 issues a read command to the interface 29.
On receiving the read command issued from the PC 60 via the interface 29, the controller 26 reads out the data of a fixed length block 66 having the structure shown in FIG. 15(b), from the magnetic disk 23.
The PC 60 receives the data read out by the controller 26 from the interface 29, and temporarily stores the data of the fixed length block 66 composed of the 1GOP 64 and the dummy data 65, into the buffer 76. The PC 60 then carries out the AV decoding of the 1GOP 64 portion alone stored in the buffer 76, at the rate of 30 frames per second or the like, and thereby displays the data on the monitor connected to the PC 60.
FIG. 15(c) shows a time chart of simultaneous recording and reproducing of fixed length blocks 66 each composed of a 1GOP 64 and dummy data 65.
In the prior art system, the operation is divided into time intervals of length T (T indicates a predetermined time length). The PC 60 controls the HDD 10 so as to record and reproduce the data once in each time interval T. That is, as shown in FIG. 15(c), the PC 60 controls the HDD 10 so as to record a fixed length block 66a and reproduce a fixed length block 66b in a time interval T.
FIG. 16 shows reproducing operation. In the reproducing, the PC 60 controls the HDD 10 so as to read out the AV data stored on the magnetic disk 23 on a fixed length block 66 basis. The PC 60 reads out the data of a fixed length block 66 once in a time interval T as indicated by read-out 68a, and then stores the data in the buffer 76. Also in the next time interval T, the PC 60 reads out the data of a fixed length block 66 once as indicated by read-out 68b, and then stores the data in the buffer 76. Further, in the second next time interval T, the PC 60 reads out the data of a fixed length block 66 once as indicated by read-out 68c, and then stores the data in the buffer 76.
At the same time, the PC 60 successively reads and decodes the AV data stored in the buffer 76. That is, the PC 60 successively reads and decodes the data on a 1GOP (containing the AV data of 15 frames, in this prior art example) basis, as indicated by output 69a, 69b, and 69c. 
As such, the PC 60 controls the HDD 10 so as to record and reproduce the data once in each time interval T on a fixed length block 66 basis.
Even in a more general case of multi-channel processing in which the PC 60 and the HDD 10 record and reproduce, for example two channels of AV data simultaneously, the PC 60 controls the HDD 10 so as to record and reproduce the data of each channel once in each time interval T.
In such multi-channel processing by the PC 60, the processing is carried out cyclically for each channel in an order previously determined by the PC 60. This situation is described below for the case of multi-channel processing for four channels.
Here, process A indicates the process of recording (or reproducing) of AV data 1. Process B indicates the process of recording (or reproducing) of AV data 2. Process C indicates the process of recording (or reproducing) of AV data 3. Process D indicates the process of recording (or reproducing) of AV data 4.
The PC 60 carries out the processes A, B, C, and D of recording into (or reproducing from) the HDD 10 in this order in a time interval T on a fixed length block 66 basis. Also in the next time interval T, the PC 60 carries out the processes A, B, C, and D of recording into (or reproducing from) the HDD 10 in this order on a fixed length block 66 basis. Further, in the second next time interval T, the PC 60 carries out the processes A, B, C, and D in this order.
As such, in multi-channel processing by the PC 60, the processing is carried out cyclically for each channel in each time interval T in the predetermined order.
That is, even in multi-channel processing in which the PC 60 and the HDD 10 record and reproduce multi-channel AV data, the PC 60 controls the HDD 10 so as to record and reproduce the data of each channel once in each time interval T in a predetermined order, whereby continuous transfer of the AV data is ensured for each channel.
As described above, the PC 60 controls the HDD 10 so as to record and reproduce the AV data of each channel once and only once in each time interval T on a fixed length block 66 basis. At that time, when it takes a longer time in recording to or reproducing from the magnetic disk 23 than normal cases, such a case can occur that the recording or reproducing of the data of a fixed length block 66 is not completed during the time interval T. An example of such cases is that a defective sector is found during the recording or reproducing in the magnetic disk 23 of the HDD 10, and that the HDD 10 retries the process.
In such a case, as shown in the time chart of FIG. 17(a), the process of recording or reproducing in the HDD 10 continues after the elapse of time T. Thus, the delay time interval 70 has a time length of T′ longer than T. This delay propagates to the subsequent processes of recording and reproducing.
In another case, as shown in FIG. 17(b), in a delay time interval 71, a recording process has been delayed, whereby the subsequent reproducing process cannot complete during the time interval T. This causes a drop in the data as indicated by a drop 72.
In any case, when recording and/or reproducing processes are not completed during the time interval T, caused is a drop in the data or a delay in the subsequent processes of recording and reproducing.
FIG. 18 shows reproducing operation in case that the process has been delayed as described above. The data of a fixed length block 66 is not read out from the HDD 10 as indicated by read-out 73. In spite of this, the data of the fixed length block 66 needs to be output as indicated by output 74. Thus, a drop occurs in the AV data output from the PC 60. That is, when a recording or reproducing process in the magnetic disk 23 is not completed during the time interval T, a drop occurs in the AV data during the recording or reproducing process. This impairs continuous transfer of the AV data.
Further, as mentioned above, defective regions occur in the magnetic disk 23 by aging and the like during the use of the HDD 10.
Described below is the management of such defective regions carried out by the PC 60 and the HDD 10.
The PC 60 and the HDD 10 are provided with error recovery functions in order to improve the reliability in recording and reproducing.
Such error recovery functions include: a retry process in which recording or reproducing is retried in the region where an error has occurred; and an alternation process and an LBA reassignment process in which the LBA having been assigned to the region where an error has occurred is reassigned to another region, whereby the use of the region where an error has occurred is terminated.
The retry process carried out by the HDD 10 is described below first.
When an error has occurred during the recording or reproducing of a sector indicated by an LBA specified by the PC 60, the controller 26 moves the magnetic head 24 slightly, and then retries the recording or reproducing. Such retry processes are repeated a predetermined times until normal recording or reproducing is achieved.
In case that normal recording or reproducing is not achieved even after the retry processes of the predetermined times, the controller 26 determines the sector as defective, and thereby invokes an alternation process described below. The alternation process is carried out within the HDD 10.
FIG, 19 illustrates an alternation process. FIG. 19(a) shows the correspondence between LBAs and magnetic disk 23 regions before the alternation process. FIG. 19(b) shows the correspondence between LBAs and magnetic disk 23 regions after the alternation process. FIG. 19(c) shows the magnetic disk 23.
In order to record or reproduce AV data to or from the HDD 10, the PC 60 notifies an LBA to be recorded or reproduced, to the HDD 10. The controller 26 of the HDD 10 carries out the recording or reproducing the data in a sector specified by the LBA. That is, the controller 26 has a table of correspondence between LBAs and magnetic disk 23 regions.
In normal recording or reproducing, the correspondence table is as shown in FIG. 19(a). That is, LBAs 1-6 sequentially correspond to the sectors in a region A of the magnetic disk 23. An LBA 7 corresponds to a sector B of the magnetic disk 23. LBAs 8-12 sequentially correspond to the sectors in a region C of the magnetic disk 23.
It is assumed that an error has occurred during the recording to the LBA 7. That is, during the recording to the sector B, data was not recorded normally even after the retry processes of the predetermined times. Alternatively, it is assumed that during the reproducing from the sector B, retry processes have been repeated the predetermined times or more.
In such a case, the controller 26 determines the sector B of the magnetic disk 23 as defective, and thereby updates the above-mentioned correspondence table so that an alternate sector B′ in the alternate region is used in place of the sector B.
As described above, the magnetic disk 23 is provided with a predetermined region used for alternation processes. A sector within this region is used as an alternate sector in an alternation process.
That is, as shown in FIG. 19(b), the correspondence table is updated such that the LBA 7 indicates the sector B′.
After this process, when receiving from the PC 60 an instruction of recording or reproducing in LBA 7, the controller 26 carries out the recording or reproducing in the sector B′ instead of the sector B.
As such, in the alternation process, when a defective sector is found, the controller 26 updates the correspondence table between LBAs and magnetic disk 23 sectors, whereby after that, an alternate sector in the alternate region is used instead of the defective sector.
As a result of the alternation process, such a separate sector B′ as shown in FIG. 19(c) is assigned to the LBA. This causes seek actions even in the access to consecutive LBAs, and hence degrades the continuous transfer performance in the hard disk apparatus.
FIG. 20 illustrates an LBA reassignment process carried out by the PC 60. During this reassignment process, the function of alternation process in the HDD 10 is turned off. FIG. 20(a) shows the result of an LBA reassignment process carried out when the sector indicated by the LBA 7 was defective similarly to the case of FIG. 19(b).
That is, the PC 60 has an LBA correspondence table shown in FIG. 20(a). This table corresponds LBAs used in the PC 60 to LBAs used in the HDD 10.
The sector corresponding to the LBA 7 is defective. Accordingly, access to the LBA 7 causes an access error.
When the number of such defective sectors increases to a certain level, an LBA reassignment process is carried out. The LBA reassignment process avoids the use of the defective sector B. That is, LBAs used in the PC 60 are corresponded to LBAs used in the HDD 10 as shown in FIG. 20(a). This avoids the use of the defective sector B. Further, the LBA correspondence table is generated such that the LBAs used in the PC 60 correspond to the sectors in the order of disk rotation. By virtue of this, when the PC 60 accesses the LBAs sequentially, the sectors are accessed sequentially in the order of disk rotation with skipping the defective region. This avoids the necessity of seek actions.
Nevertheless, in the prior art system for recording and reproducing AV data, when the recording is carried out on a GOP basis, recording data of fixed size is generated by adding dummy data to the GOP. This increases the size of the data, and thereby causes an idle time in the data transfer, in comparison with the case of the GOP alone.
That is, there has been the problem that the recording on a GOP basis needs adding of dummy data, and that this increases the size of the data, and thereby causes an idle time in the data transfer.
Further, there has been the problem that when the recording or reproducing is not completed during the predetermined time interval, the buffer action becomes incomplete, whereby a drop occurs in the recorded or reproduced AV data.
Furthermore, in the management of defective regions, an alternation process assigns an LBA to a separate sector as illustrated by the LBA 7 in FIG. 19(b). This causes the necessity of seek actions even in the access to consecutive LBAs. Accordingly, when the alternation processes are repeated, the number of necessary seek actions increases and thereby degrades the performance of recording and reproducing in the hard disk apparatus.
That is, there has been the problem that the alternation process degrades the performance of recording and reproducing in the hard disk apparatus.
In order to resolve the above-mentioned problems, the PC carries out an LBA reassignment process as described above. Nevertheless, this LBA reassignment process takes a long time because the data already recorded in the sectors needs to be moved to another sectors. That is, there has been the problem that the LBA reassignment process needs a long time.